In a case that reads like a movie script, a Catholic priest on Wednesday pleaded guilty to trying to help a convicted mob hitman recover a purported Stradivarius violin hidden in the wall of a house.

Eugene Klein, who had been a federal prison chaplain, admitted to conspiring in 2011 to defraud the United States by passing messages from mobster Frank Calabrese to an unnamed associate on how to get the violin out of Calabrese’s Wisconsin home.

If found and authenticated as made by 18th-century instrument maker Antonio Stradivari, such a violin would have been worth millions of dollars. Calabrese had also claimed the violin had once been owned by pianist Liberace, according to local media accounts.

Calabrese, also known as “Frankie Breeze,” was serving a life sentence at the federal prison in Springfield, Missouri, in connection with more than a dozen gangland slayings.

Federal authorities were selling his property to compensate the families of victims, and he wanted the violin recovered before the house was sold, court documents said.

Klein, 66, had been permitted to meet with Calabrese regularly to provide religious ministries, like giving communion. He knew that he was not supposed to pass messages to and from Calabrese, prosecutors said.

But Klein agreed to be a messenger, the plea agreement said. The communications included a letter concealed in religious reading materials and passed to Klein through a slot in the door of Calabrese’s prison cell, the plea agreement said.

The letter had instructions on how to find the violin, and how to get into the home.

Klein didn’t turn over the letter but admitted to telling the unnamed person what it said.

Federal authorities had found paperwork about a 1764 violin in another of Calabrese’s homes. A certificate describing the violin bore an emblem with the word “Stradivari,” but it said the violin was made by Giuseppe Antonio Artalli, court documents said.

No violin was found.

Thomas Durkin, Klein’s attorney, questioned whether the violin ever even existed, and he compared the hunt for it to “looking for a unicorn,” according to the Chicago Sun-Times.

Durkin was not immediately available for comment.

Klein, of Springfield, Missouri, faces up to five years in prison and a $250,000 fine when he is sentenced on June 23.